Sealing element for pipes and methods for using

ABSTRACT

A sealing device for shutting down a pipe, comprising an expandable cylindrical sleeve ( 1 ), which is designed with a conical interior, and is provided with radially through-going slots ( 3 ) extending in the sleeve&#39;s longitudinal direction from each of the sleeve&#39;s end surfaces ( 4,5 ), with slots from opposite end surfaces being arranged between one another. A rod ( 2 ) extends through the sleeve ( 1 ), where the rod ( 2 ) is provided with a conical portion with an outside adapted to the sleeve&#39;s conical inside, and where the rod&#39;s conical portion has a smallest diameter smaller than or equal to the sleeve&#39;s smallest inner diameter in its non-expanded form and a largest diameter equal to or larger than the sleeve&#39;s largest inner diameter in its expanded form. When inserting the sealing device, the rod ( 2 ) is passed in the sleeve&#39;s ( 1 ) longitudinal direction, thus causing the rod&#39;s conical portion to come into contact with and be pressed against the sleeve&#39;s inner surface, with the result that the sleeve is expanded and comes into contact with the pipe wall.

The invention relates to a sealing device for shutting down a pipe,especially suitable for shutting down a pipe in a well, and methods forinserting and removing the sealing device.

On many occasions it is desirable to shut down a pipe in a well. In oilwells, this procedure is employed in a number of cases when a shutdownis required against reservoir pressure, between different zones in thewell, when acid or other liquids have to be injected, in the event ofperforation of the pipe, jointing of formations or when the well has tobe completely shut in.

For shutting down oil wells-it is known to use various different typesof sealing devices as a part of a plug. These plugs with sealing devicesare lowered into the well to the desired depth, whereupon they areactivated so as to seal against pressure. In many cases these plugs canalso be recovered by means of a suitable pulling tool. The commonfeature of such plugs is that the sealing device consists of anexpandable elastic packing element, an anchoring part and a part thatkeeps the plug locked in an expanded position.

Before insertion in the well, an external running tool is connected tothe plug. When the plug has been lowered to the desired position, therunning tool is activated and an axial force is generated, which pullson an internal rod on the plug while an external sleeve is pushedtowards the plug. A relative motion is then generated between rod andsleeve, which is utilised for fastening the plug's anchoring part to thecasing in the well, and for expanding the elastic sealing elementagainst the casing. When the insertion operation is completed, therunning tool is uncoupled from the plug by severing a calibratedconnection between plug and running tool. This is usually achieved dueto the fact that the relative force between running tool and plugexceeds the breaking strength of the connection. A locking mechanism canensure that the anchoring element is not moved relative to the pipe wallin the well, and that the sealing element stays expanded. The plug thusremains in place in order to seal the pipe for the desired period. Whenremoving the plug after it has performed its sealing function, a runningtool is lowered which meets the top of the plug and engages with it.When it is pulled upwards, the locking mechanism can be disconnected,thus enabling the anchoring to be contracted radially, whereupon theplug can be withdrawn from the well.

When high pressure and temperatures are encountered, various types ofmechanical barrier are often used round a sealing element of elasticmaterial. This barrier may have several functions; to reduce the gapbetween the plug's outer diameter and the casing's inner diameter, torestrict the area of expansion of the expandable sealing material and toshield the sealing material from pressure and temperature variations.This may be necessary in order to prevent an alteration in the materialcharacteristic of the sealing materials. When the seal is exposed tohigh pressure, the elastic material in the seal is pressed against thebarrier. These barriers may be composed of a spring, which is cast intothe sealing element, as links that are expanded axially, or as variouskinds of rings or bands that can be expanded radially. If this barrierhas openings, damage could occur to the sealing surface. This will be aproblem particularly in the event of pressure pulses or varyingtemperatures. When the packer moves on account of temperature changes orpressure changes, therefore, gashes or cracks can easily occur in theelastic material, which may result in leakages.

When there is a large clearance between the casing and the plug's outerdiameter, a relatively large amount of elastic sealing material has tobe used in order to compensate for the volume required to fill theclearance between plug and pipe. When there is a large clearance betweenthe casing and the plug's outer diameter, the elastic sealing materialwill be subjected to enormous strain on account of the relatively largevariation that exists between the expanded and non-expanded shape. Inaddition, as mentioned earlier metallic extrusion barriers are used,which have to be expanded in the same way. Under the influence oftemperature, elastic materials may also behave in such a manner thatthey will be capable of flowing out through any splits in the barrier.In many cases the elastic element will also undergo changes, resultingin cracking of the material over the course of time. This may give riseto leakages. In addition, over the course of time a permanentdeformation will occur in the sealing element, which may make isdifficult to withdraw the plug from the well, since the sealing elementdoes not return to its original diameter.

Examples of this type of plug with substantially an elastic sealingmaterial and barriers are disclosed in patents GB 2 308 138A, EP A2 155413, U.S. Pat. No. 5,226,492 and GB 2 296 520 A.

In U.S. Pat. No. 2,247,325 a slightly different type of packing elementis disclosed comprising a conical rod, which pushes the packing elementoutwards and into engagement with a casing. U.S. Pat. No. 1,092,540describes a packer consisting of separate conical packing elements,which, when pushed together, are pressed outwards into engagement with acasing.

The object of the present invention is to achieve a sealing device,which is particularly suitable for use in a well, which is resistant tohigh pressure and temperatures and possibly also an acid environment,which avoids the problem of sealing material changing from an elastic toa brittle material and cracking during use, and which avoids the problemof permanent deformation of an elastic material, which creates problemsif the sealing device has to be removed.

The object is achieved with a sealing device for shutting down a pipeand methods for inserting and removing a sealing device according to theinvention, where the characterising features of the sealing device andmethods for inserting and removing the sealing device are indicated inthe accompanying claims.

A sealing device according to the invention is particularly suitable foruse in a well, but may also be employed in other types of pipes. Asealing device according to the invention for shutting down a pipecomprises an expandable cylindrical sleeve, which is designed with aconical interior. The sleeve is provided with radially through-goingslots extending in the sleeve's longitudinal direction from each of thesleeve's end surfaces, with slots from opposite end surfaces beingarranged between one another and creating a sleeve in a meandering form.The sealing device further comprises a rod extending through the sleeve.The rod is provided with a conically shaped portion, the outside ofwhich is adapted to the conical inside of the sleeve. The rod's conicalportion has a smallest diameter smaller than or equal to the sleeve'ssmallest inner diameter in its non-expanded form and a largest diameterequal to or larger than the sleeve's largest inner diameter in itsexpanded form. When inserting the sealing device, the rod is passed inthe sleeve's longitudinal direction so that the conical portion of therod comes into abutment against the sleeve's inner surface and expandsthe sleeve with the result that it comes into abutment against the pipewall.

The invention will now be described in greater detail with reference toaccompanying drawings, which illustrate an embodiment, in which:

FIG. 1 illustrates the sealing device in expanded form,

FIG. 2 is a perspective view of what is illustrated in FIG. 1,

FIG. 2B is a perspective view similar to FIG. 2 of another embodiment.

FIG. 3 is a section along the sealing device's longitudinal axis of thesealing device in expanded form located in a pipe,

FIG. 3B is a section similar to FIG. 3, of another embodiment.

FIG. 4 illustrates the sealing device in a non-expanded form beforeinsertion in a pipe,

FIG. 5 is a perspective view of what is illustrated in FIG. 4,

FIG. 6 is a section along the sealing device's longitudinal axis of thesealing device in a non-expanded form located in a pipe.

Corresponding elements have been given identical reference numerals inall the figures.

A sealing device according to the invention comprises an expandablecylindrical sleeve 1. The sleeve is designed with an inner conicalsurface and provided with radially through-going slots 3 extending inthe sleeve's longitudinal directions from each of the sleeve's endsurfaces 4,5, with slots from opposite end surfaces being arrangedbetween one another. This gives the sleeve a meandering form in itscircumference. The sealing device further comprises a rod 2 extendingthrough the sleeve's 1 inner cavity. The length of the rod is preferablyat least twice the length of the sleeve in the longitudinal direction.The rod 2 is provided with a conically shaped portion, with an outsideadapted to the conical inside of the sleeve, where the conical portionof the rod has a smallest diameter smaller than or equal to the sleeve'ssmallest inner diameter in its non-expanded form and a largest diameterequal to or larger than the sleeve's largest inner diameter in itsexpanded form. The rod's conical portion may, for example, be a conicalportion machined in the rod by milling, turning or the like or aconically shaped part mounted on the rod. When inserting the sealingdevice, the rod 2 is passed in the sleeve's 1 longitudinal direction,thus causing the conical portion of the rod to come into abutmentagainst the sleeve's inner surface and expand the sleeve so that itcomes into engagement with the pipe wall. A force may be applied to therod that is sufficient to cause plastic deformation of the sleeve, butnot sufficient to cause a rupture in the sleeve material.

The sealing device may be inserted in a pipe R in a well by applying acompressive or tensile force to the rod. If the sealing device has to beinserted by the application of compressive forces, the running tool may,for example, comprise a striking tool. In this case the sealing deviceis inserted in such a manner that the end of the rod 2 where the conicalportion has the largest diameter is facing the running tool. The rod'sconical surface will be pushed into the sleeve 1 and expand it until thedesired force is applied to the sleeve and the sealing device withstandthe desired pressure. Alternatively, the sealing device may be insertedby applying a tensile force to the rod. In this embodiment the narrowend of the rod's conical portion will be facing a running tool. Therunning tool will exert a tensile force on the rod, thus achieving thedesired direct action and a secure frictional connection between sleeveand pipe wall. A low-friction coating may be applied to the outside andinside respectively of the rod and the sleeve in order to facilitate theinsertion of the conical part of the rod in the sleeve. Running toolsfor inserting sealing devices in pipes in different manners are knownand do not form any part of the present invention and therefore receiveno further mention.

Tests have been carried out with a model of a sealing device accordingto the invention. The test was carried out with a model of the sealingdevice on the scale 1:1 and comprised an expandable sleeve and a rodwith a conical surface for expansion of the sleeve. These were placed ina pipe with an inner diameter larger than the sleeve's outer diameter ina non-expanded form. The sleeve was manufactured in an expanded form,which will be explained in greater detail below. The material in themodel's conically shaped sleeve and rod was ST-52, which is steel withyield strength of approximately 320 N/mm², a breaking point between500-600 N/mm² and an elongation at break of approximately 21%. The angleof the conical area of the rod in the model was 1:10. During the test ahydraulic piston was employed and 1.0 ton (2204 lb) was applied to therod in order to expand the sleeve. The rod was then pushed into thesleeve with a force of 20 tons (44093 lb). On the application of such aforce on the sealing device, sleeve and rod were secure in the pipe dueto frictional forces and the pipe was sealed against water penetration.The rod was then pushed out of contact with the sleeve by applying aforce of 10 tons (22046 lb). After the rod had been pushed away from thesleeve, the sleeve was pushed through an outer pipe with an internalconical area with an angle 1:13. During the test a hydraulic piston wasemployed and a force of 1.0 ton (2204 lb) was applied in order tocompress the sleeve to a non-expanded diameter.

In a preferred embodiment of the sealing device the sleeve 1 may beprovided in its outer surface with devices that ensure a tight seal,preferably one or more grooves 6 for one or more sealing elements. Thegroove and sealing element are advantageously Continuous in the sleeve'scircumference in order to ensure a tight sealing device after insertingthe sealing device in a pipe. In an alternative embodiment the sleevemay be provided in its outer surface with outwardly protruding ribs 15,as shown in FIG. 2B, which, when the sleeve comes into abutment againstthe pipe wall, lead to a small local deformation of the pipe wall andthe rib, thereby creating a tight connection between the sleeve and thepipe wall. These outwardly projecting ribs are also advantageouslycontinuous about the sleeve's circumference. Both groove with sealingelement and outwardly projecting ribs are designed in such a manner thatthey do not cause any major problems if the sealing device has to beremoved, when the sleeve is radially compressed.

In order to ensure a tight connection between the sleeve and the rod'sconical surface, the sleeve may be provided in its inner surface withone or more grooves for a sealing element. In this case groove andsealing element are also advantageously continuous in the circumferenceof the rod, and the inner surface of the sleeve. Sealing between rod andsleeve may also be achieved by applying a coating externally on therod's conical portion, or alternatively the sleeve's internal conicalsurface. This coating may be of a softer material, thus enabling it tofill any gaps or spaces between sleeve and rod. Sealing can also beachieved by means of direct metallic contact between sleeve and rod. Aperson skilled in the art will appreciate that a tight connectionbetween rod and sleeve can be achieved in a number of alternative ways.

In a preferred embodiment, devices that ensure a tight seal, preferablygroove 6 for locating a sealing element have a width representing amaximum of 80%, but most preferred under 50% of the sleeve's width fromthe inner point of a slot 12 to the opposite end surface of the sleeve.These percentages are intended as guidelines for designing the sleeve,but are not absolute. Preferred ratios will vary with the type ofmaterial employed in the sleeve and the conditions under which thesealing device has to operate. What is important is that the width ofthe sleeve from the groove in the sleeve to the sleeve's end edge is ofsuch an extent that the sealing material in the groove is effectivelyshielded from the influence of pressure variations. A ratio of this kindbetween the length of the sleeve and that of the sealing element alsoensures that any deformations of the sealing device will besubstantially absorbed in the sleeve and not in the sealing element.This guarantees stability in the sealing device sealing properties.Since the seating material constitutes a minor part of the sealingdevice's outer surface, this also avoids problems due to permanentdeformation of the sealing material when the sealing device is removedonce it has completed its intended purpose.

In a preferred embodiment of a sealing device according to the inventionthe sleeve 1 is manufactured by machining a pipe, with an outer diameterlarger than the sleeve's outer diameter into a non-expanded form.Machining should be understood to refer amongst other things to theremoval of material from the pipe in order to form an inner conicalsurface and slots 3 in the sleeve, by means of, for example, milling,turning, sawing or the like, and other machining in order to form asleeve according to the invention. Following the machining, the sleeve 1may be compressed. With a force that creates plastic deformation into anon-expanded form. Alternatively, the sleeve 1 may be compressed byapplying an external pipe, which keeps the sleeve 1 compressed, wherethe sleeve 1 in the non-expanded form of the sleeve is compressed to anouter diameter that makes it possible to have the sleeve 1 located in adesired position in a pipe R in a well. This may be a diameter that issmaller than the pipe R since, in order to be located in the desiredposition, the sealing device may possibly have to be passed throughequipment previously located in the well such as valves, sensors or thelike, which may have a smaller inner diameter than the pipe.

In an embodiment, as shown in FIG. 3B, of the sealing device the rod 2may be designed with at least one bore 16 in its longitudinal direction.In such an embodiment the sealing device may be employed in connectionwith production from or shutdown of zones in a well. Well fluid or otherequipment may then be passed through the sealing device through the borein the rod. In an embodiment where the rod has no bore in itslongitudinal direction, the sealing device may act as a productionpacker.

According to an embodiment the sealing device may further comprise afirst support sleeve 8 with an inner diameter approximately equal to therod's largest diameter, and comprising an end portion 14 facing andattached to the sleeve's first end 4. The first support sleeve's 8 endportion 14 is designed with radially through-going slots 10 extending inthe first support sleeve's 8 longitudinal direction. The slots 10 in thefirst support sleeve 8 are arranged in the extension of the sleeve'sslots 3, which extend from the sleeve's first end 4. The sealing devicefurther comprises a second support sleeve 9 of similar design to thefirst support sleeve 8, but oppositely directed and where an end portion13 is facing and attached to the sleeve's second end 5. The secondsupport sleeve's 9 end portion 13 is also designed with radiallythrough-going slots 10 extending in the second support sleeve's 9longitudinal direction and where the slots 10 in the second supportsleeve 9 are arranged in extension of the sleeve's slots 3, which extendin the sleeve's 1 longitudinal direction from the second end 5. In thisembodiment the sealing device also comprises a guide 11, which isarranged between the first support sleeve 8 and the rod 2, and has aninner conical surface, where, during insertion of the sealing device,the guide's 11 inner conical surface abuts against the narrow part ofthe rod's 2 conical portion.

The individual elements in a sealing device according to the inventionhave now been described. A schematic description will be given below ofa method for inserting and removing the sealing device.

A preferred method for inserting a sealing device according to theinvention comprises the following steps. The sealing device in anon-expanded form is attached to a running tool, whereupon the runningtool with the sealing device is passed to the desired position in thewell. At the desired position in the well, the running tool is securedin relation to the pipe wall. By means of the running tool the rod 2 isthen passed in the sleeve's 1 longitudinal direction, thus causing thesleeve 1 to be expanded and come into abutment against the pipe wall,the connection between sealing device and running tool being broken bythe application of a predefined power transmission from the running toolto the sealing device. The sealing device is thereby attached to thepipe wall with a frictional connection, whereupon the running tool iswithdrawn from the pipe.

In the method for removing a plug according to the invention, a runningtool is lowered to the sealing device in the well and affixed thereto.The running tool then applies a force to the rod 2, with the result thatthe rod 2 is moved out of abutment against the sleeve 1. Furthermore, anaxial force is applied to the sleeve 1, resulting in a radialcompression of the sleeve 1 to an outer diameter, which enables thesleeve 1 to be withdrawn from the well. A radial compression of thiskind can be achieved by an outer pipe being pressed down over the sleeve1 in the sealing device, but a person skilled in the art will understandthat this can be done in other ways. After the sleeve has beencompressed, the sealing device with the running tool are withdrawn fromthe pipe.

The invention has now been described by means of embodiments. Withregard to the embodiment, a number of variations and modifications maybe envisaged within the scope of the invention as it is defined in thefollowing claims. For example, the sleeve 1 may be designed with outerribs in its surface for increased friction between pipe wall and sealingdevice, thereby offering greater resistance to movement of the sealingdevice in the pipe's longitudinal direction. A sealing device accordingto the invention may have a number of areas of application; it may beused for shutdown of a well or a pipeline, it may be used in all kindsof plugs, be it plugs that have to be capable of being removed or onlypushed down into the well after use or permanent plugs. The sealingdevice according to the invention may also be used for shutdown ofindividual zones in a well, while fluid is flowing through a pipe in theextension of the bore in the sealing device according to the invention.This may be done, for example, where parts of a casing are damaged.Several sealing devices according to the invention may be placed oneafter the other at desired intervals, thus permitting fluid shutdownbetween the sealing devices, while well fluid is passed through the rod.The sealing device according to the invention may also be envisagedemployed for securing an extension pipe to the casing in the productionzone. In this case the sealing device will be an integrated part of theanchoring. The sealing device may also be used to close off fluid andpressure between production tubing and casing.

1. A sealing device for shutting down a pipe, comprising an expandablecylindrical sleeve, which is designed with a conical interior, and a rodextending through the cylindrical sleeve, where the rod is provided witha conical portion with an outside adapted to the sleeve's conical insideand with a smallest diameter smaller than or equal to the sleeve'ssmallest inner diameter in its non-expanded form and a largest diameterequal to or larger than the sleeve's largest inner diameter in itsexpanded form, where, when inserting the sealing device, the rod ispassed in the cylindrical sleeve's longitudinal direction, thus causingthe rod's conical portion to come into contact with and be pressedagainst the cylindrical sleeve's inner surface, with the result that thecylindrical sleeve is expanded and comes into contact with the pipewall, characterised in that the cylindrical sleeve is provided withradially through-going slots extending in the sleeve's longitudinaldirection from each of the cylindrical sleeve's end surfaces, with slotsfrom opposite end surfaces being arranged between one another.
 2. Asealing device according to claim 1, characterised in that the sealingdevice further comprises a first support sleeve with an inner diameterapproximately equal to the rod's largest diameter, and comprising an endportion facing and attached to the cylindrical sleeve's first end, wherethe end portion is designed with radially through-going slots extendingin the first support sleeve's longitudinal direction, where the slots inthe first support sleeve are arranged in the extension of thecylindrical sleeve's slots, a second support sleeve with an innerdiameter approximately equal to the rod's largest diameter, andcomprising an end portion facing and attached to the cylindricalsleeve's second end, where the end portion is designed with radiallythrough-going slots extending in the second support sleeve'slongitudinal direction, where the slots in the second support sleeve arearranged in extension of the cylindrical sleeve's slots, and a guide,which is arranged between the first support sleeve and the rod, and hasan inner conical surface, where, during insertion of the sealing device,the guide's inner conical surface abuts against the narrow part of therod's conical portion.
 3. A sealing device according to claim 2,characterised in that the cylindrical sleeve's outer surface is providedwith one or more grooves for one or more sealing elements.
 4. A sealingdevice according to claim 3, characterised in that the rod's conicalportion and/or the cylindrical sleeve's inner surface is provided withone or more grooves for one or more sealing elements.
 5. A sealingdevice according to claim 4, characterised in that the grooves forlocating the sealing elements have a width representing a maximum of80%, preferably less than 50% of the cylindrical sleeve's width frominner point of a slot to the opposite end surface of the cylindricalsleeve.
 6. A sealing device according to claim 5, characterised in thatthe cylindrical sleeve is manufactured by machining a pipe that has anouter diameter larger than the cylindrical sleeve's outer diameter in anon-expanded form, with subsequent radial compression.
 7. A sealingdevice according to one of the claims 1-6, characterised in that thecylindrical sleeve is provided with outwardly projecting ribs in itsouter surface.
 8. A sealing device according to one of the claims 1-6,characterised in that the rod has at least one through-going bore in itslongitudinal direction.
 9. A sealing device according to claim 8,characterised in that the cylindrical sleeve is provided with outwardlyprojecting ribs in its outer surface.
 10. A method for inserting asealing device according to one of the claims 1-6, characterised by thefollowing steps: a) the sealing device in non-expanded form is attachedto a running tool, b) the running tool with the sealing device arepassed to the desired position in the well, c) the running tool is heldin the correct position in relation to the pipe wall, d) by means of therunning tool, the rod is passed in the sleeve's longitudinal direction,thus causing the sleeve to be expanded and come into abutment againstthe pipe wall, and thereby be attached to the pipe wall with africtional connection, the connection between sealing device and runningtool being broken by the transmission of a desired force from therunning tool to the sealing device, e) the running tool is withdrawnfrom the pipe.
 11. A method according to claim 10, characterized in thatthe cylindrical sleeve is provided with outwardly projecting ribs in itsouter surface.
 12. A method according to claim 10, characterized in thatthe rod has at least one through-going bore in its longitudinaldirection.
 13. A method according to claim 12, characterized in that thecylindrical sleeve is provided with outwardly projecting ribs in itsouter surface.
 14. A method for removing a sealing device according toone of the claims 1-6, characterised by the following steps: x) arunning tool is lowered to the sealing device in the well and affixedthereto, y) the running tool applies a force to the rod, with the resultthat the rod is moved out of abutment against the cylindrical sleeve, z)an axial force is then applied to the cylindrical sleeve, resulting in aradial compression of the cylindrical sleeve, v) the sealing device withthe running tool are withdrawn from the pipe.
 15. A method according toclaim 14, characterized in that the cylindrical sleeve is provided withoutwardly projecting ribs in its outer surface.
 16. A method accordingto claim 14, characterized in that the rod has at least onethrough-going bore in its longitudinal direction.
 17. A method accordingto claim 16, characterized in that the cylindrical sleeve is providedwith outwardly projecting ribs in its outer surface.